1. Field of the Invention
This invention relates in general to certain new and useful improvements in catheter systems, and more particularly, to a method and assembly for securing a flexible and somewhat stretchable silicone rubber tube to a plastic fitting.
2. Brief Description of the Prior Art
Intraveneous catheter systems are widely used in surgical and post-surgical procedures and particularly in many hospital environments. For example, central venal access catheters are commonly employed in cardiac post-surgical procedures. One end of the catheter tube is introduced into the body venal system through an incision formed in the body, and the other end which remains external to the body, is provided with a fitting and a removeable cap on the fitting. In this way, the cap can be removed for connection to a source of intraveneously injected fluid.
One of the preferred tubings used in the catheter system is a silicone rubber tube. This tube has been selected due to its human tissue compatability, and resiliency and flexibility as well as the fact that it is capable of being effectively used in sterile environments. However, it has also been recognized that one of the principal problems in the use of this tubing is the securement of the tubing in a fluid tight condition to a rigid plastic fitting such as a polyethylene or polyvinyl or polypropylene fitting. A fluid tight seal between the fitting or so-called "luer" and the tubing is essential in order to preclude leakage of any intraveneous fluid to be injected. The fluid tight seal is equally important to preclude the body cavity from being open to the external environment through an ineffective seal between the tubing and the fitting.
In order to obtain a relatively fluid tight seal, many prior art fittings have resorted to the use of so-called "barbs" e.g. spaced apart cylindrically shaped outwardly projecting ribs on the cylindrically shaped stem of the fitting. These ribs or barbs protrude beyond the stem surface to extend into and slightly deform the silicone rubber tube. It has been found, however, that these barbs do not necessarily provide a fluid tight seal and in many cases, after a short period of use, will tend to cut into the silicone rubber tubing and thereby ultimately lead to a fracture of the tubing.
In other attempts to obtain a fluid tight seal, sutures were used for wrapping about the rubber tubing as it extended over a stem on the fitting to thereby tightly compress the rubber tubing about the stem of the fitting, at least in the regions of the sutures. This wrapping technique in combination with adhesives has also been employed. This technique for adhering the rubber tubing to the plastic stem of the fitting results in cosmetically inferior joinder regions. Further, this technique results in a more costly seal and hence a more costly device due to ecessive labor time for wrapping the sutures. It has also been shown with silicone rubber that sharp sutures can cut into the silicone rubber after a period of time.
U.S. Pat. No. 1,723,273 to Irwin discloses a coupling member used for catheter tubes with a central hub containing a plurality of barbs to retain a tube inserted over the coupling member. A metallic locking collar having a tapered end is slid over the tube to hold it in place.
U.S. Pat. No. 626,210 to Deitz also shows a coupling member with only one barb on the end thereof and with a locking collar positioned interior to the barb. In this case, the locking collar extends only over a very small portion of the tube.
U.S. Pat. No. 161,492 to Dayton also discloses a hose joint which uses a single locking collar.